Exhaust mufflers often include a sound absorbing material within the interior of the muffler to absorb and attenuate the sound made by the escaping gases that pass through the muffler. Many types of exhaust mufflers are produced by mechanically joining multiple pieces to form a muffler shell. For example, one common type of exhaust muffler is known as a spun muffler. Spun mufflers are made by forming a sheet of material into the desired shape to form the muffler body and attaching end caps to this body by welding or crimping to form the muffler shell. Another common type of exhaust muffler is a clamshell muffler, which is assembled by joining an upper section to a lower section by welding or crimping. Both spun mufflers and clamshell mufflers are generally divided into multiple chambers by baffles, or partitions, and contain perforated inlet and outlet pipes that span between the chambers to input and exhaust the gases from the muffler.
A common material used to fill exhaust mufflers is continuous fibrous materials. The fibers usually fill one or more of the muffler chambers, and are often inserted into the muffler in a texturized, or “bulked up” form. In one approach, the bulked up fibers are forced into the assembled muffler shell through either the inlet or outlet pipe. For best performance, it is important to provide generally uniform distribution and filling density of the bulked up fibers when they are forced into the cavities of the assembled muffler shell. There is a need for an improved muffler filling method that better performs this function.